Positive Indication of Latching in an Inner and Outer Tube Assembly, Especially for Downhole Assemblies

ABSTRACT

A latch body ( 10 ) incorporates spring-loaded latches ( 11 ) and ( 12 ) which secure the inner tube assembly in place by latching against a shoulder in an adaptor coupling. At the lower end of the latch body ( 10 ) there are water inlet ports ( 13 ), a landing shoulder ( 14 ) and water outlet ports ( 15 ). The valve mechanism ( 20 ) includes a piston ( 21 ) slidable within upper cylinder ( 22 ) above the inlet ports ( 12 ) which has a recess ( 23 ) at its upper end for receiving a ball ( 24 ) and a sealing flange ( 25 ), at its lower end. The upper cylinder ( 22 ) has a recess ( 26 ) in which part of the ball can seat to cock the piston. A second cylinder ( 27 ) between the inlet ports ( 13 ) and outlet ports ( 15 ) carries a spring guide ( 28 ) having a valve seat ( 30 ) at its upper end. A spring ( 31 ) acts against the sealing flange ( 25 ). When the piston ( 21 ) is cocked, the sealing flange ( 25 ) is adjacent to and spaced from the valve seat ( 30 ) and is forced spaced from the valve seat ( 30 ) and is forced against the valve seat ( 30 ) by water pressure to close the valve and uncock the piston.

FIELD OF INVENTION

This invention relates to core drilling and more particularly to a latch body and valve mechanism which provides positive indication of the correct latching of an inner tube assembly when the landing shoulder of the latch body seats in the landing ring of the outer tube.

BACKGROUND ART

When a drill run has been completed and the inner tube is ready to be pulled, an overshot on a wire line is dropped down the borehole and latches itself onto the spear point. By pulling the overshot upwards, the latches connecting the inner tube assembly to the adaptor coupling are closed unlatching the inner tube assembly which is then retrieved. When the inner tube assembly is being relocated in the outer tube there is a need to provide a positive indication that the inner tube is properly latched.

SUMMARY OF INVENTION

According to one aspect of the invention there is provided a latch body and valve mechanism for providing a positive indication of the correct latching of an inner tube assembly, the latch body having a water inlet port, a latching shoulder below the water inlet port and a water outlet port below the latching shoulder, and wherein the valve mechanism comprises a piston moveable within a first cylinder above the inlet port between an uncocked position and a cocked position in which a cocking mechanism restricts movement of one end of the piston into the first cylinder, the piston having a sealing flange at its other end, a second cylinder between the inlet port and outlet port having a spring guide therein, the spring guide having a valve seat facing the sealing flange and an opening at its other end leading to the outlet port, a spring within the spring guide adapted to bear against the flange of the piston, the arrangement being such that when the piston is in the cocked position the flange is within the top of the second cylinder adjacent to but spaced from the valve seat and prevented from moving away from the valve seat by the cocking mechanism, the flange being forced against the valve seat by water pressure to close the valve and uncock the piston.

Preferably, the cocking mechanism comprises a ball adapted to seat in a recess at the top of the piston away from the flange and the first cylinder has a recess for receiving part of the ball, the arrangement being such that the piston is cocked by withdrawing it from the cylinder so that the ball may sit partly in the recess and bear against the end of the piston to prevent the piston from retracting into the cylinder.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a latch body and valve latch mechanism according to one embodiment of the invention together with a latching tool,

FIG. 2 is a cross-sectional view of the latch body and valve mechanism shown in FIG. 1,

FIG. 3 is an exploded view of the latch body and valve mechanism shown in FIG. 2,

FIG. 4 is a partly sectioned view of the valve mechanism with the latching tool inserted and the latch body in a horizontal position,

FIG. 5 is a view similar to FIG. 4 with the latching tool rotated so as to cock the valve mechanism,

FIG. 6 is a partly sectioned view of the latch body in its vertical operating disposition, with the valve mechanism in its cocked position,

FIG. 7 is a view similar to FIG. 6 showing the valve mechanism being pressurised, and

FIG. 8 shows the valve mechanism in its inoperative position after positive latching has been indicated.

BEST MODE FOR CARRYING OUT THE INVENTION

The tubular latch body 10 shown in FIGS. 1 to 3. 10 incorporates spring-loaded latches 11, 12 which secure the inner tube assembly 41 in place by latching against a shoulder in an adaptor coupling (not shown). At the lower end of the latch body 10 there are water inlet ports 13, a landing shoulder 14, water outlet ports 15 and a lower housing 16 to which an inner tube (not shown) is connected.

The latch body 10 has a spear point 17 and a sleeve portion 18 which has a pair of opposed slots 43 through which the latches 11, 12 project. At the lower end of each latch 11 and 12 there is an inwardly sloping shoulder 19.

The spring loaded latches 11 and 12 are biased to their latched position but will only truly latch when the inner tube is correctly seated when the landing shoulder 14 of the latch body seats in the landing ring of the outer tube (not shown). When this happens, all water flow must pass through the water ports 13 and 15 and the latches 11 and 12 are situated below the internal shoulder in the adaptor coupling which will prevent the inner tube assembly from rising.

When a run has been drilled and the inner tube assembly is ready to be pulled, an overshot on a wire line rope is dropped down and latches itself onto the spear point 17. By pulling the rope attached to the overshot with a wire line winch, the sleeve portion 18 is pulled upwardly and the bottom of each of the slots 43 engage the sloping shoulders 19 to force the latches 11 and 12 into the latch body 10 thereby unlatching the inner tube assembly which can then be retrieved.

The valve mechanism 20 shown in its uncocked position in FIG. 2 is located within the lower end of the latching body 10 and includes a piston 21 slidable within an upper or first cylinder or chamber 22 located above the inlet ports 13. The piston 21 has a recess 23 at its upper end for receiving a ball 24 and a sealing flange 25 at its lower end. The upper cylinder 22 has a recess 26 in which part of the ball 24 can seat.

Beneath the inlet ports 13 there is a lower or second open-ended cylinder 27 and within the lower cylinder 27 there is a spring guide 28 having a base 29, and a valve seat 30 at its upper end. Within the guide 28 there is a spring 31. The base 29 seats against annular shoulder 33 of the lower housing 6.

As shown in FIG. 8, when the ball 24 is sitting in the piston recess 23, the spring 31 is not under high compression and water can flow into the inlet ports 13, over the spring 13, through the spring guide 28 and out the opening 32 in the base 29 of the spring guide 28 to the outlet ports 15.

The valve mechanism 20 is shown in its cocked position in FIG. 6. The valve mechanism 20 is cocked with the latching body 10 in a horizontal position with the recess 26 lowermost by inserting a latching tool or lever 50 into the uppermost inlet port 13 and catching the working tab 52 of the latching tool 50 on the top face of the flange 25 as shown in FIG. 4. The piston 21 is then forced down against the force of the spring 31 by rotating the handle 51 of the lever 50. When the piston 21 has been forced far enough down, the ball 24 will partly seat in the upper cylinder recess 26 under the influence of gravity and leave sufficient of the ball exposed so as to jam the piston 21 in a position where the flange 25 is still clear of the valve seat 30 but as the flange 25 is in the top part of the lower cylinder 27 water can not flow from the inlet ports 13 through the spring guide 28 to the outlet ports 15.

The valve mechanism 20 is shown pressurised in FIG. 7. The flange 25 has been forced down by the rising water pressure causing closure of the passageway in the spring guide 28 from the port 13 to the outlet port 15. The flange 25 of the piston 21 is thus forced against the valve seat 30 and the piston 21 is held there by water pressure on top of the flange 25 acting to compress the spring 31. At this stage the ball 24 falls out of the recess 26 into the recess 23 on the top of the piston 21 (see arrow in FIG. 7).

No water can flow through the water ports 13 and 15 and no water can pass the seal between the flange 25 and the valve seat 30 and if there is correct latching this causes a rise in water pressure indicating the correct seating and latching of the inner tube. After a predetermined rise in water pressure, the water pump is stopped, the pressure in the system vented to atmosphere and the piston 21 forced to the top of its stroke again by the spring 31 thereby allowing water to flow through the ports 13 and 15 and drilling can commence in the sure and certain knowledge no mis-latch has occurred. 

1. A latch body and valve mechanism for providing a positive indication of the correct latching of an inner tube assembly having a water inlet port above a latching shoulder and a water outlet port below the latching shoulder, and wherein the valve mechanism comprises a piston moveable within a first cylinder above the inlet port between an uncocked position and a cocked position in which a cocking mechanism restricts movement of one end of the piston into the first cylinder, the piston having a sealing flange at its other end, a second cylinder between the inlet port and outlet port having a spring guide therein, the spring guide having a valve seat facing the sealing flange and an opening at its other end leading to the outlet port, a spring within the spring guide adapted to bear against the flange of the piston, the arrangement being such that when the piston is in the cocked position the flange is within the top of the second cylinder adjacent to but spaced from the valve seat and prevented from moving away from the valve seat by the cocking mechanism, the flange being forced against the valve seat by water pressure to close the valve and uncock the piston.
 2. A latch body and valve mechanism according to claim 1 wherein the cocking mechanism comprises a ball adapted to seat in a recess at the top of the piston away from the flange and the first cylinder has a recess for receiving part of the ball, the arrangement being such that the piston is cocked by withdrawing it from the cylinder so that the ball may sit partly in the recess and bear against the end of the piston to prevent the piston from retracting into the cylinder.
 3. A latch body and valve mechanism according to claim 2 wherein the closure of the valve enables the ball to move from the recess in the first cylinder to the recess in the piston so that upon release of the water pressure the piston will be forced by the spring into the first cylinder with the sealing flange of the piston moving away from the valve seat to open the valve.
 4. A latch body and valve mechanism according to claim 1 further including a sleeve portion above the valve mechanism having a pair of opposed slots through which latches project to engage an adaptor coupling.
 5. A latch body and valve mechanism according to claim 4 wherein each latch has an upper shoulder adapted to engage the adaptor coupling and lower sloping shoulders adapted to be engaged by the lower end of the slot so to retract the latch when the sleeve portion is raised.
 6. A latch body and valve mechanism according to claim 2 wherein the piston is cocked by laying the latch body and valve mechanism horizontal, inserting a rotatable tool into the inlet port to engage the upper surface of the sealing flange of the piston, and rotating the tool so that the piston is moved against the action of the spring to allow the ball to partly enter the recess in the first cylinder. 